A wood fiber-based superhydrophobic coating and a method for preparing the same
By utilizing a method for preparing wood fiber-based superhydrophobic coatings and employing a low-eutectic solvent and polydimethylsiloxane crosslinking technology, the high cost and complex preparation of existing superhydrophobic materials have been addressed, enabling the construction of low-cost and environmentally friendly superhydrophobic coatings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-20
- Publication Date
- 2026-03-24
AI Technical Summary
Existing superhydrophobic materials are mainly petroleum-based products, which are costly and have complex preparation processes. The use of fluorinated chemicals is toxic to the environment. Nanocellulose is expensive and requires costly drying methods for preparation, resulting in insufficient market competitiveness.
A method for preparing a wood fiber-based superhydrophobic coating is adopted, which involves swelling a thermo-milling mechanical slurry with a eutectic solvent, spraying nanoscale dispersed filter residue onto the substrate surface, and crosslinking it with a mixed solution of polydimethylsiloxane and curing agent. This method simplifies the preparation process, reduces the amount of organic solvent used, and reduces toxicity.
It reduces preparation costs, simplifies process steps, reduces the use of toxic chemicals, and enables the construction of low-cost superhydrophobic coatings, which has both environmental and practical application value.
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Figure CN118357137B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of superhydrophobic coating technology, and in particular to a wood fiber-based superhydrophobic coating and its preparation method. Background Technology
[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.
[0003] Superhydrophobic materials possess self-cleaning properties and have wide applications in architectural coatings, automotive painting, and marine coatings. Currently, commercially available superhydrophobic materials are primarily petroleum-based products, modified with fluorinated chemicals, which pose significant toxicity during production and use. Therefore, researchers have attempted to use renewable and environmentally friendly materials—nanocellulose—as the main material to prepare superhydrophobic coatings. However, nanocellulose itself is expensive, and the preparation process requires costly drying methods such as spray drying, freeze drying, and supercritical drying to obtain the necessary micro / nanostructures for superhydrophobic materials, resulting in high costs and making the products uncompetitive in the market. Therefore, finding low-cost superhydrophobic material substrates and simplified methods for constructing micro / nanostructures are urgent problems to be solved. Summary of the Invention
[0004] In view of this, the present invention provides a wood fiber-based superhydrophobic coating and its preparation method, which solves the problems of expensive raw materials for environmentally friendly superhydrophobic materials, complicated construction steps and high cost of superhydrophobic coatings in the prior art.
[0005] In a first aspect, the present invention provides a method for preparing a wood fiber-based superhydrophobic coating, comprising the following steps:
[0006] The dried thermomechanical slurry is added to a eutectic solvent to swell, then heated to react. After the reaction is terminated, it is filtered while hot, and the filter residue is washed with hot ethanol. The filter residue is then mechanically dispersed in ethanol to the nanoscale and allowed to settle. The bottom settling layer is sprayed onto the surface of the substrate, and then a mixed solution of polydimethylsiloxane and curing agent is sprayed onto the surface of the substrate again. After drying, the product is obtained.
[0007] Preferably, in the step of adding the dried thermomechanical slurry to a eutectic solvent for swelling, the swelling time is 0.5 to 3 hours and the swelling temperature is 10 to 35°C.
[0008] Preferably, the mass ratio of the dried thermomechanical slurry to the eutectic solvent is 1:(20-200); the reaction temperature of the heating reaction is 90-140°C, and the reaction time is 0.5-3h.
[0009] Preferably, the eutectic solvent includes hydrogen bond acceptors, monoacid hydrogen bond donors, polyacid hydrogen bond donors, and alcohols.
[0010] Furthermore, the hydrogen bond acceptor is choline chloride; the monoacid hydrogen bond donor includes one or more of p-toluenesulfonic acid, lactic acid, acetic acid, formic acid, or propionic acid; the polyacid hydrogen bond donor includes one or more of citric acid, oxalic acid, malic acid, or tartaric acid; and the alcohol is ethylene glycol.
[0011] Furthermore, the mass ratio of the hydrogen bond acceptor, the monoacid hydrogen bond donor, the polyacid hydrogen bond donor, and the alcohol is 1:(0.5-2.5):(0.5-2.5):(0.5-1.5).
[0012] Preferably, the step of terminating the reaction specifically involves adding 2 to 5 times the volume of ethanol, a low-eutectic solvent, to the mixed solution after the reaction has been heated.
[0013] Preferably, the temperature of the hot ethanol is 40–70°C.
[0014] Preferably, in the step of mechanically dispersing the filter residue in ethanol to the nanoscale, the ratio of the dry weight of the filter residue to the amount of ethanol is 0.5 g: (150-250) mL; the mechanical dispersion method includes any one of ultrasonic crushing, high-pressure homogenization or high-speed stirring.
[0015] Preferably, the settling time is 3 to 12 hours; the spray volume ratio of the bottom settling layer to the mixed solution of polydimethylsiloxane and curing agent is (4 to 6): 1.
[0016] Preferably, in the mixed solution of polydimethylsiloxane and curing agent, the solvent is cyclohexane or tetrahydrofuran; the ratio of polydimethylsiloxane, curing agent and solvent is 1g:0.1g:(3-10)mL.
[0017] Preferably, the drying temperature after the mixed solution of polydimethylsiloxane and curing agent is sprayed onto the substrate surface again is 60-100°C, and the drying time is 2-8 hours.
[0018] Secondly, the present invention provides a wood fiber-based superhydrophobic coating prepared by the above preparation method.
[0019] Compared with the prior art, the present invention has achieved the following beneficial effects:
[0020] The micro-nano structure of the superhydrophobic coating of this invention is constructed from nanoscale wood fibers, using thermomechanical pulp as raw material, which is low in cost and requires minimal equipment during preparation. This invention achieves the construction of the superhydrophobic coating through a two-step spraying method, significantly reducing the amount of toxic organic solvents (cyclohexane or tetrahydrofuran) used in the spraying step, resulting in low toxicity. The first spray uses ethanol as a solvent, making it environmentally friendly. The production process of the superhydrophobic coating of this invention does not contain highly toxic chemicals, and the preparation method is simple and easy to implement, possessing practical application value. Attached Figure Description
[0021] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.
[0022] Figure 1 This is a test diagram of the contact angle of the superhydrophobic coating in Embodiment 1 of the present invention;
[0023] Figure 2 This is a scanning electron microscope image of the superhydrophobic coating of Embodiment 1 of the present invention. Detailed Implementation
[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0025] This invention provides a method for preparing a wood fiber-based superhydrophobic coating, comprising the following steps:
[0026] The dried thermomechanical slurry is added to a eutectic solvent to swell, then heated to react. After the reaction is terminated, it is filtered while hot, and the filter residue is washed with hot ethanol. The filter residue is then mechanically dispersed in ethanol to the nanoscale and allowed to settle. The bottom settling layer is sprayed onto the surface of the substrate, and then a mixed solution of polydimethylsiloxane and curing agent is sprayed onto the surface of the substrate again. After drying, the product is obtained.
[0027] This invention first swells lignin in a thermomechanical pulp using a eutectic solvent, followed by a heated reaction. During this reaction, lignin dissolves in the eutectic solvent, while cellulose remains undissolved. The filter residue after hot filtration is a loose fibrous mass with a small amount of lignin-linked fibers on its surface. This is then mechanically dispersed to obtain nanoscale wood fibers, which settle in ethanol. The settled layer is primarily composed of nanoscale wood fibers, with ethanol as the dispersant. This bottom settled layer is directly sprayed onto the substrate as a spraying agent. The nanoscale wood fibers within this layer construct the micro / nano structure of the superhydrophobic coating. Because non-toxic ethanol is used instead of toxic reagents such as tetrahydrofuran or cyclohexane, the amount of toxic reagents used in preparing the superhydrophobic coating from nanocellulose can be significantly reduced. This invention also involves a second spraying of a mixed solution of polydimethylsiloxane and a curing agent onto the substrate surface after the first spraying. Since the second spraying agent does not need to disperse the main micro / nano structure material but only serves to cover and crosslink, only a small amount is required. This method can significantly reduce the amount of toxic organic reagents used. After drying and curing, polydimethylsiloxane (PDMS) crosslinks to form a monolithic structure, firmly adhering to the substrate and encapsulating the nanoscale wood fibers. PDMS provides hydrophobicity, while the nanoscale wood fibers provide the micro / nano structure; together, they create a superhydrophobic coating.
[0028] The present invention does not impose special restrictions on the source of the thermomechanical pulp. For example, it can be obtained from low-cost thermomechanical pulp obtained by crushing agricultural and forestry waste such as corn stalks, wheat straw, wheat stalks, and wood scraps.
[0029] In this invention, the dried thermomechanical pulp is added to a eutectic solvent for swelling, with a swelling time of 0.5–3 hours and a swelling temperature of 10–35°C. Swelling at a lower temperature allows the eutectic solvent to fully penetrate into the wood fibers. Direct high-temperature reaction would cause the surface lignin to dissolve and block the original pore structure, hindering the penetration of the eutectic solvent.
[0030] The mass ratio of the dried thermomechanical slurry to the eutectic solvent of the present invention is 1:(20-200), more preferably 1:(40-100).
[0031] The eutectic solvent of this invention comprises hydrogen bond acceptors, monoacid hydrogen bond donors, polyacid hydrogen bond donors, and alcohols. Further, the hydrogen bond acceptor is choline chloride; the monoacid hydrogen bond donors include one or more of p-toluenesulfonic acid, lactic acid, acetic acid, formic acid, or propionic acid, which have low pKa values and can provide an acidic environment; the polyacid hydrogen bond donors include one or more of citric acid, oxalic acid, malic acid, or tartaric acid, which can be grafted onto wood fibers to give them strongly hydrophilic carboxyl groups, facilitating the aggregation of nanoscale wood fibers into spherical structures during spraying in ethanol; the alcohol is ethylene glycol, which has certain steric hindrance and low viscosity, reducing lignin aggregation and decreasing the size of lignin during precipitation, achieving nanoscale and polyhydroxyl content, thus facilitating further utilization of lignin.
[0032] The preferred mass ratio of the hydrogen bond acceptor, monoacid hydrogen bond donor, polyacid hydrogen bond donor and alcohol in this invention is 1:(0.5-2.5):(0.5-2.5):(0.5-1.5); for example, it can be selected as 1:2:2:1 or 1:1:1:1, etc.
[0033] In this invention, the reaction temperature of the heating reaction is 90–140°C, and the reaction time is 0.5–3 h.
[0034] The specific steps for terminating the reaction in this invention are as follows: adding 2 to 5 times the volume of ethanol, a low-euclidean solvent, to the mixed solution after the reaction has been heated.
[0035] In this invention, the temperature of the hot ethanol is 40–70°C. Washing the filter residue with hot ethanol is primarily to reduce viscosity and increase the filtration and washing speed. During the washing process, lignin dissolved in the eutectic solvent can be washed from the surface of the loose wood fiber filter residue into the filtrate, achieving the separation of the lignin bulk and the wood fibers.
[0036] The filtrate obtained by hot filtration in this invention contains a high content of lignin. Dropping this filtrate into water precipitates small-sized lignin particles with a high phenolic hydroxyl content. In this invention, the rate at which the filtrate is dropped into water is 5–50 mL / min, more preferably 10–30 mL / min. This invention does not impose any special restrictions on the subsequent utilization of the obtained lignin particles.
[0037] In the step of mechanically dispersing the filter residue in ethanol to the nanoscale in this invention, the ratio of the oven-dry weight of the filter residue to the amount of ethanol is 0.5 g:(150-250) mL; the mechanical dispersion method includes any one of ultrasonic crushing, high-pressure homogenization, or high-speed stirring. Nanoscale wood fibers can be obtained through mechanical dispersion, which serve as the main building material for superhydrophobic coating micro / nano structures.
[0038] In this invention, the settling time is 3–12 hours; the spray volume ratio of the bottom settling layer to the mixed solution of polydimethylsiloxane and curing agent is (4–6):1. Because the first spray in this invention has already sprayed the nano-sized wood fibers onto the substrate surface, the second spray does not require a large amount of solvent to disperse the nano-sized wood fibers. Therefore, the solvent usage in the second spray is very low, resulting in a significant reduction in overall toxicity between the two steps.
[0039] In the mixed solution of polydimethylsiloxane and curing agent described in this invention, the solvent is cyclohexane or tetrahydrofuran, which have good solubility for both polydimethylsiloxane and curing agent, and are also relatively volatile, both being low-toxicity solvents. The ratio of polydimethylsiloxane, curing agent, and solvent used in this invention is 1g:0.1g:(3-10)mL.
[0040] In this invention, the mixed solution of polydimethylsiloxane and curing agent is sprayed again onto the substrate surface, and then dried at a temperature of 60–100°C for 2–8 hours. This process ensures complete solvent evaporation and cross-linking curing of PDMS to form a cohesive whole, firmly bonding it to the substrate.
[0041] The present invention also provides a wood fiber-based superhydrophobic coating prepared by the above preparation method.
[0042] The technical solution of the present invention will be further described below with reference to specific embodiments.
[0043] Example 1
[0044] This embodiment provides a method for preparing a wood fiber-based superhydrophobic coating.
[0045] (1) Mix 10g choline chloride, 20g p-toluenesulfonic acid, 20g citric acid and 10g ethylene glycol, heat to 80℃ to dissolve into a transparent solution, which is the eutectic solvent. Cool to room temperature for later use.
[0046] (2) Add 1g of dried poplar wood hot grinding mechanical slurry to the above eutectic solvent, stir at 300 rpm for 1h, then heat to 100℃ and keep warm for 2h to obtain the reaction solution.
[0047] (3) Add 200 mL of ethanol to the reaction solution to terminate the reaction. After stirring evenly, filter while hot to obtain filtrate and filter residue. Wash the filter residue multiple times with 500 mL of ethanol at 60 °C. Perform the operation of step (4) on the obtained filter residue. Add the filtrate dropwise to water at a rate of 20 mL / min. Filter and dry to obtain lignin with high phenolic hydroxyl content. Collect it. This example does not further utilize it.
[0048] (4) Disperse 0.5g of filter residue (dry weight) again into 200mL of ethanol and ultrasonically break it up for 10 minutes at 800W.
[0049] (5) After ultrasonic crushing, let it stand and settle for 3 hours. Take 5 mL of the bottom nano-wood fiber settling layer and spray it onto the glass substrate surface using a 0.3 mm spray gun.
[0050] (6) Spray 1 mL of a cyclohexane solution of polydimethylsiloxane and curing agent (containing 0.2 g polydimethylsiloxane and 0.02 g curing agent) onto the glass surface after spraying the nano-wood fiber settling layer in step (5).
[0051] (7) After spraying twice, the glass is dried in an 80℃ oven for 4 hours to obtain a superhydrophobic surface with a contact angle of 151°. Figure 1 As shown. Figure 2 The image shown is a scanning electron microscope image of the superhydrophobic coating in this embodiment. As can be seen, the coating surface has a rough structure.
[0052] Example 2
[0053] This embodiment provides a method for preparing a wood fiber-based superhydrophobic coating.
[0054] (1) Mix 10g choline chloride, 20g p-toluenesulfonic acid, 20g malic acid and 10g ethylene glycol, heat to 80℃ to dissolve into a transparent solution, which is the eutectic solvent. Cool to room temperature for later use.
[0055] (2) Add 1g of dried poplar wood hot grinding mechanical slurry to the above eutectic solvent, stir at 300 rpm for 1h, then heat to 110℃ and keep warm for 1.5h to obtain the reaction solution.
[0056] (3) Add 200 mL of ethanol to the reaction solution to terminate the reaction. After stirring evenly, filter while hot to obtain filtrate and filter residue. Wash the filter residue multiple times with 500 mL of ethanol at 60 °C. Perform the operation of step (4) on the obtained filter residue. Add the filtrate dropwise to water at a rate of 20 mL / min. Filter and dry to obtain lignin with high phenolic hydroxyl content. Collect it. This example does not further utilize it.
[0057] (4) Disperse 0.5g of filter residue (dry weight) again into 200mL of ethanol and homogenize under high pressure for 10 minutes.
[0058] (5) After standing for 4 hours, take 5 mL of the bottom nano-wood fiber settling layer and spray it onto the glass substrate surface using a 0.3 mm spray gun.
[0059] (6) Spray 1 mL of a tetrahydrofuran solution of polydimethylsiloxane and curing agent (containing 0.2 g polydimethylsiloxane and 0.02 g curing agent) onto the glass surface after spraying the nanofiber settling layer in step (5).
[0060] (7) After spraying twice, the glass is placed in an 80° oven and dried for 4 hours to obtain a superhydrophobic surface with a contact angle of 150°.
[0061] Example 3
[0062] This embodiment provides a method for preparing a wood fiber-based superhydrophobic coating.
[0063] (1) Mix 15g choline chloride, 15g acetic acid, 15g oxalic acid and 15g ethylene glycol, heat to 80℃ to dissolve into a transparent solution, which is the eutectic solvent. Cool to room temperature for later use.
[0064] (2) Add 1.5g of dried poplar wood hot grinding mechanical slurry to the above eutectic solvent, stir at 300 rpm for 1h, then heat to 100℃ and keep warm for 2h to obtain the reaction solution.
[0065] (3) Add 200 mL of ethanol to the reaction solution to terminate the reaction. After stirring evenly, filter while hot to obtain filtrate and filter residue. Wash the filter residue multiple times with 500 mL of ethanol at 60 °C. Perform the operation of step (4) on the obtained filter residue. Add the filtrate dropwise to water at a rate of 20 mL / min. Filter and dry to obtain lignin with high phenolic hydroxyl content. Collect it. This example does not further utilize it.
[0066] (4) Disperse 0.5g of filter residue (dry weight) again into 200mL of ethanol and ultrasonically break it up for 10 minutes at 800W.
[0067] (5) After standing for 3 hours, take 4 mL of the bottom nano-wood fiber settling layer and spray it onto the glass substrate surface using a 0.3 mm spray gun.
[0068] (6) Spray 1 mL of a cyclohexane solution of polydimethylsiloxane and curing agent (containing 0.3 g polydimethylsiloxane and 0.05 g curing agent) onto the glass surface after spraying the nano-wood fiber settling layer in step (5).
[0069] (7) After spraying twice, the glass is placed in an 80°C oven and dried for 4 hours to obtain a superhydrophobic surface with a contact angle of 153°.
[0070] Example 4
[0071] This embodiment provides a method for preparing a wood fiber-based superhydrophobic coating.
[0072] (1) Mix 10g choline chloride, 20g propionic acid, 20g tartaric acid and 10g ethylene glycol, heat to 80℃ to dissolve into a transparent solution, which is the eutectic solvent. Cool to room temperature for later use.
[0073] (2) Add 1g of dried poplar wood hot grinding mechanical slurry to the above eutectic solvent, stir at 300 rpm for 1h, then heat to 100℃ and keep warm for 2h to obtain the reaction solution.
[0074] (3) Add 200 mL of ethanol to the reaction solution to terminate the reaction. After stirring evenly, filter while hot to obtain filtrate and filter residue. Wash the filter residue multiple times with 500 mL of ethanol at 60 °C. Perform the operation of step (4) on the obtained filter residue. Add the filtrate dropwise to water at a rate of 20 mL / min. Filter and dry to obtain lignin with high phenolic hydroxyl content. Collect it. This example does not further utilize it.
[0075] (4) Disperse 0.5g of filter residue (dry weight) again into 200mL of ethanol and ultrasonically break it up for 10 minutes at 800W.
[0076] (5) After standing for 5 hours, take 6 mL of the bottom nano-wood fiber settling layer and spray it onto the glass substrate surface using a 0.3 mm spray gun.
[0077] (6) Spray 1 mL of a cyclohexane solution of polydimethylsiloxane and curing agent (containing 0.2 g polydimethylsiloxane and 0.02 g curing agent) onto the glass surface after spraying the nano-wood fiber settling layer in step (5).
[0078] (7) After spraying twice, the glass is placed in an 80°C oven and dried for 4 hours to obtain a superhydrophobic surface with a contact angle of 152°.
[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a wood fiber-based superhydrophobic coating, characterized in that, Includes the following steps: The dried thermomechanical slurry is added to a eutectic solvent to swell, then heated to react. After the reaction is terminated, it is filtered while hot, and the filter residue is washed with hot ethanol. The filter residue is then mechanically dispersed in ethanol to the nanoscale and allowed to settle. The bottom settling layer is sprayed onto the substrate surface, and then a mixed solution of polydimethylsiloxane and curing agent is sprayed onto the substrate surface again. After drying, the product is obtained. The eutectic solvent includes hydrogen bond acceptors, monoacid hydrogen bond donors, polyacid hydrogen bond donors, and alcohols; The temperature of the hot ethanol is 40~70℃; In the mixed solution of polydimethylsiloxane and curing agent, the solvent is cyclohexane or tetrahydrofuran; the ratio of polydimethylsiloxane, curing agent and solvent is 1g : 0.1g : (3~10)mL.
2. The preparation method according to claim 1, characterized in that, In the step of adding the dried thermomechanical slurry to the eutectic solvent for swelling, the swelling time is 0.5~3h and the swelling temperature is 10~35℃; the mass ratio of the dried thermomechanical slurry to the eutectic solvent is 1:(20~200); the reaction temperature of the heating reaction is 90~140℃ and the reaction time is 0.5~3h.
3. The preparation method according to claim 1, characterized in that, The hydrogen bond acceptor is choline chloride; the monoacid hydrogen bond donor includes one or more of p-toluenesulfonic acid, lactic acid, acetic acid, formic acid, or propionic acid; the polyacid hydrogen bond donor includes one or more of citric acid, oxalic acid, malic acid, or tartaric acid; the alcohol is ethylene glycol; the mass ratio of the hydrogen bond acceptor, monoacid hydrogen bond donor, polyacid hydrogen bond donor, and alcohol is 1 : (0.5~2.5) : (0.5~2.5) : (0.5~1.5).
4. The preparation method according to claim 1, characterized in that, The specific steps for terminating the reaction are as follows: add 2 to 5 times the volume of ethanol, a low-euclidean solvent, to the mixed solution after the reaction has been heated.
5. The preparation method according to claim 1, characterized in that, In the step of mechanically dispersing the filter residue in ethanol to the nanoscale, the ratio of the dry weight of the filter residue to the amount of ethanol is 0.5 g: (150~250) mL; the mechanical dispersion method includes any one of ultrasonic crushing, high-pressure homogenization or high-speed stirring.
6. The preparation method according to claim 1, characterized in that, The settling time is 3-12 hours; the spray volume ratio of the bottom settling layer to the mixed solution of polydimethylsiloxane and curing agent is (4-6):
1.
7. The preparation method according to claim 1, characterized in that, The drying temperature after the mixed solution of polydimethylsiloxane and curing agent is sprayed onto the substrate surface again is 60~100℃, and the drying time is 2~8h.
8. The wood fiber-based superhydrophobic coating prepared by the preparation method according to any one of claims 1 to 7.